Effect of the substitution of S for Se on the structure and non-linear optical properties of the glasses in the system Ge0.18Ga0.05Sb0.07S0.70−xSex

Glasses in the system Ge–Ga–Sb–S/Se have been elaborated with different S/Se ratios in order to increase the non-linear optical properties of these glasses. We report results of a systematic study examining the relationship of the physical properties to the structure of the glasses in the system Ge0.18Ga0.05Sb0.07S0.70−xSex with x = 0, 0.02, 0.05, 0.10, 0.20, 0.30 and 0.40 where the replacement of S by Se has been made. The non-linear refractive index has been measured using the Z-scan technique, with picosecond pulses emitted by a 10 Hz Q-switched mode-locked Nd-Yag laser at 1064 nm under conditions suitable to characterize ultrafast non-linearities. The decrease of the glass transition temperature, the increase of the non-linear refractive index and of the density with the progressive replacement of S by Se have been correlated along with the red shift of the absorption band gap, to associated structural reorganization. A corresponding progressive decrease of corner-sharing GeS4/2 and the formation of mostly two edge-sharing Ge2S4S2/2, S3Ge–S–GeS3 as well as mixed GeS4−xSex units have been identified by Raman spectroscopy.